Scanning process



Nov; 29, 1938. A J, AWLEY 2,138,089

SCANNING PROCESS Original Filed Sept. 10, 1929 Patented Nov. 29, 1938UNITED snares SCANNING PROCESS Aloysius J. Cawley, Pittston, Pa.

Application September 10, 1929, Serial No. 391,541 Renewed August 18,1937 6 Claims.

This is a continuation-in-part application of my applications SerialNumber 383,390, filed August 3,1929 and Serial Number 384,687, filedAugust 9, 1929.

The invention relates generally to television, or the transmission ofvisual images from place to place by means of electromagnetic waves.However, electriccurrents traversing wired circuits may be used, ifdesired.

More particularly, the invention is concerned with a new scanning means.This term is well known to those skilled in the art, and is the processby which the difierent portions'of the image are brought successivelyinto contact with the photoelectric element at the transmitting stationin order thatan image variation may be impressed upon theelectromagnetic waves that are being transmitted. At the receivingstation the scanning apparatus distributes the image-varied light of aneon or other light to the proper portions of the image successively.

Broadly, thescanning means herein described covers the movement inopposite directions of two media each bearing a series of lightpermeable '7 areas in such manner that there is a continuousintersection of the different members of the light permeable series.These media may be in many different forms.

Two disks are described which are mounted upondifierent shafts and theirmargins made to overlap each other, permitting a constant intersectionof light permeable areas producing a travelling light dot or point.

A great advantage is that throughout the entire'contact area of the twomoving media, whether they be disks, tapes, or other, there is aplurality of images formed, and all of these images arein exactsynchronism. Means are disclosed showing the manner of projectingseveral of those synchronous images superposed upon the picture screen,and thus the brightness of the image may be increased to any extentdesired by projecting as many images superposed as desired. Thus a greatdrawback in television is overcome, namely the extreme faintness of theimage, which usually permits only silhouettes to be transmitted.

Ma'nyspecial means are shown for moving two disks in oppositedirections, including ordinary gear wheels and also worm gearingmechanisms. Those gearings are shown for both separately mounted disksand for concentrically mounted ones.

Some of the many, many variations in the arrangement of the lightpermeable areas carried by the two oppositely moving media areillustrated and described.

Special means are shown for projecting the many synchronous imagesproduced by the two moving media I are illustrated. These may beprojected directly upon the screen or indirectly, by first passing thelight beam through a light reflecting means.

Another object of the invention is the use of a third moving medium inthe form of a mask, which prevents the passage of light throughundesirable portions of the light permeable media.

Still another object of the invention is the formation of several imagesat the broadcasting station and placing a photoelectric cell in theimage field of each image, together with scanning media similar to thatdescribed in this specification. This increases the television signal.strength many fold.

For a more complete understanding of the in vention, reference is to behadto the following description and claims taken in connection with theaccompanying drawing, in which like characters of reference denotecorresponding parts in all of the views, and in which,

Figure 1 Ban elevational view of an arrangement employingthe use ofribbons or tapes as moving media carrying light permeable areas. It alsoillustrates the means for projecting several of the synchronous imagessuperposed upon a screen, and illustrates the use of reflectors for thispurpose.

Figure 2 is an elevational view of an arrange ment employing a thirdmoving medium in the form of a mask, for the purpose of cutting out thelight of undesirable points of intersection of the light permeableareas, andalso the viewing of more thanone of the synchronous images.

Figure 3a, illustrates two media bearing light permeable areas in theform of lines intersecting each other at an angle of ninety degrees. Theexactsynchonism of the two images is illustrated by means of the arrows.The moving mask is also illustrated.

Figure 3b is an illustration of an apparatus similar to that of Figure3a, but there are more light permeable areas on the two media.

Figure illustrates two media carrying light permeable areas placed atdifferent angles, and. one of those media moving at a speed greatlybelow that of the other. No mask is necessary with this arrangement.

Figure 1 illustrates .a pair of media in the form of two. tapes orfilmswhich may be modified motion picture films. All throughout the areaof contact of the two media A and B, as before stated, there is a seriesof images produced that are in absolute synchronism. In the case of filmmedia A and B, these would be in a straight line, as shown in Figure 3.They present an elegant opportunity of securing any desired brightnessof image. It is simply necessary to project one upon the other upon ascreen. This may be done in the disk and cylinder method also, but thereis a certain curving of the images, as around the circumference of thedisk, while the tapes are in a straight line. However, the method maywell be used with the disks or cylinders. Power is applied in any mannerdesired to shaft 2. Bevel gears 31, 3e, 3g, 3h cause drums E and D tomove, and they in turn move film B. Worm gearing 4d and 40 cause drums Dand E to move at a speed which is much slower than that of the other twodrums. The drums D and E cause film or tape A to move at a speed that isequal to the number of pictures transmitted per second times the widthof a picture. A face view of the films A and B is shown in Figure 30 atthe right hand portion. Here it will be noticed that series a, a, etc.,are placed a picture width apart and are at right angles to thehorizontal. Series b, b, b", etc., are spaced at such a distance thatonly one area b will come into relation to area a at any time. Thearrows indicate the direction of motion of the dot, or light pointformed by the intersection of the scanning lines, which determines theimages. It is very important to notice that there is a series of imagesin synohronism, or in other words, there is a row of images all of whichare exactly alike all along the course of the films. This is veryimportant, as they may be projected one upon the other upon a screen.Neon or other lamps 5 are placed one behind each image area and theirlight shines through and reaches the lens elements 9, which act toproject and superpose the images upon the screen Hi. This is shown atthe lower portion of Figure 1. If it is desired to project images fromboth the upper and lower portion of the films, a pair of reflectors,such as prisms l9 at both the top and the bottom of the figures projectand superpose all images upon If] at the right. Any degree ofillumination is, therefore possible with the apparatus.

Figure 2 shows an arrangement wherein the media. assume the form of twofilms moving in opposite directions at a speed which is almost the same.The speed of one is equal to that of the other plus the number of imagestransmitted per second times the width of a picture. This methodnecessitates the use of a mask, which is illustrated together with itsmeans of moving it. Power is applied to shaft 2 by any means desired andbevel gears, 3e, 3], 3g, and 3h cause drums D, E, C and D to move inopposite directions. The gearing is such that B moves faster than A bythe above mentioned amount in order that the lines that are drawn orscanned by the intersection 2' of the two series of light permeableareas may be drawn at successive intervals across the image area. Wormgearing 4d and 40 cause drums C and E to move film M which carriesopaque masking areas as illustratedat the bottom row of frames inFigures 3a and 3b. Here again, neon lamps 5 pass their light throughcontiguous or adjacent image areas and a series of synchrronous imagesare produced, i. e., a row of images will appear along the tapes, all ofwhich images are alike. Or, this may be better described by saying thatthere will be a row of adjacent moving pictures moving in exact step allalong the tape. This will be made clearer by reading a description ofFigures 3a, 3b and 30 below. Mask M moves at a speed equal to the numberof pictures transmitted per second multiplied by the width of a picture.It is to be noted that in all of those scanning arrangements that theonlydifference between the scanning means at the transmitter andreceiver is in the employment of photoelectric cells at the transmitterand of neon lamps at the receiver. It is to be noted also that the mediaat the transmitting station and that at the receiving station move inexact .synchronism. However, as the invention is not concerned with theproduction of a synchronizing apparatus, nor of a radio or broadcastingmeans, no illustration is given covering either of these. The scanningapparatus disclosed may be used at the receiver or transmitter.

Figures 3a, 3b and 30 cover illustrations of the various light permeableareas as employed under different conditions and arrangements. Figure 3aillustrates the two media A and B carrying light-permeable areas a andb. These media move in opposite directions. In this case the fact isbrought out that if both media moved in opposite directions at exactlythe same speed, we would have a constant passage of a light dot down aportion of the different frames f, f and f. In other words, there wouldbe simply the repeated drawing of a line at one point of the frames 1,etc. The arrows indicate the direction of the passage of the light dotor of the scanning line. The upper row of the figure at a representsthree scanning frames. It will be noted that areas a and b have just metat the upper portion of frame f. In the next row lower down, each area aand b have moved one quarter of a picture width and the arrow indicatesthat the light 2' has moved one quarter of the height of the picture. Inthe third row a and b have moved one-half a picture width and the linehas been drawn one half way down the picture, as indicated by the arrow.In the fourth row both a and b have moved three quarters of a picturewidth, and the line has been drawn three quarters down the picture asindicated by the arrow. In the fourth row a and b have moved a fullpicture width, and the line is completely drawn as indicated by thearrows. It is to be noted that all during the movement of the two media,there has been a similar and exactly synchronous movement in the framesf" and f" by other lines, similar to a and b. However, this arrangementwould never produce a picture, simply a bright line at some point ineach picture frame, I, f, 1, etc. If now either series a or b is given aspeed that is greater than that of its companion by an amount equal tothe number of pictures transmitted per second multiplied by the width ofthe picture, the repeated scanning lines will not be drawn in the sameposition as indicated by the arrows, but each successive line will bedrawn in a slightly different position, and since the whole image fieldwill be successively covered by the scanning lines, we will have animage produced. By thus increasing the speed .of a, the lines will besuccessively drawn to the left, and by increasing the speed of b theywill be drawn to the right. Here again, another defect is introducedwhich must be remedied if a perfect image is to be transmitted. As thelines shift their position to the left or right, at certain times, otherlight points, which are shown in the illustration as being coincidentwith, or covered by the frame margins, will be brought into the picturearea. Thus there would be two or more light intersecting points in theimage field, and the image would be improperly produced. To make thisclearer, let us suppose that the'apparatus is operated very slowly andthat you can actually see the lines I) that are back of medium- A. Ifthe apparatus were run slowly, the design represented by the slant lines(somewhat resembling that of wall paper) would appear to move from thetop to the bottom of the picture, i. e., coming from the top anddisappearing at the bottom. Now, when a or b is given an excess ofmotion,in addition to the movement just mentioned, this design will alsoshift to the right or left. The five views at Figure 3a illustrate thisreadily. If the two media run atequal speeds, we would have seven linesscanned or drawn, three indicated by the three arrows and four indicatedby the margin of the frames, since when there is no lateral movement,the course of the intersecting lines is clearly indicated. A thirdmedium, as described in connection with Figure 2, is introduced, whichcarries a series of opaque areas, and this is called the mask M. This isshown in the lower row of the figure. It acts to hide or mask theundesirable light dots 11 produced by undesirable intersections of linesa and b. This medium is given a speed equal to the number of picturesper second'multipliedby the width of a picture. The masking medium maybe in the form of disks, tapes, cylinders, or the like, according towhich system is used. It is evident that the excess speed of a or b overthat of its companion is the same as the-speed of the mask M. With theemployment of the mask, as described, we will have the production ofreal and perfect images. The frames f, f and f" are supposed to haveneon lamps back of them. The frames may be shifted to the right or tothe left in order to bring the picture into proper frame, as desired. Bysupplying a large number of frames, as many pictures as desired may beobtained, and they will be in exact synchronism if the frames areproperly adjusted in their" left to right position. Those images'may besuperposed upon a screen by projection, and thus it is possible to haveany degree of brightness of the image desired. Figure 3b shows-anarrangement similar to that at a with the distinction that there aretwice as many lines or light permeable areas a and I) per picture widththan in the former. The opaque portions of the mask Min the lowestportion of the figure are modified in order to cut out the increasednumber of undesirable intersections.

Figure 3c shows an entirely different arrangement than the twoillustrated at Figures 3a and 31). Here the two media move at greatlyunequal speeds. One, such as A and consequently a, is moved at a speedequal to the number of pictures per second multiplied by a picturewidth. This speed is very slow, and this particular disk may be used asthe guide to synchronism of the picture as the other medium is closelyattached to it from a speed standpoint, due to the gearing connectingboth. The other medium is moved at a great speed. The faster it isrotated, the more lines are drawn per second, and if the slow movingmedium is kept at the rate of motion corresponding to fifteen picturesper second, then We have a greater number of lines per picture, whichmeans more detail. If the speed of B is increased four-fold while thatof A remains constant, we have four times the-definition in the image.a, a, a", etc., act as rules along which I), b, b", etc., draw repeatedlines while a, etc., are slowly shifted. It is also to be noted thatincrease of speed, meaning more lines per second, also increases thebrightness. The flexibility of the system is indicated by the fact thatif youspeed up B and do not maintain that of A at the same low rate, youwill get an increased number of pictures per second, each having thesame former number of lines. This is: similar tothe old spiral holedisk. The increase of the number of lines per picture, however, is agreat advantage, as it increases detail or half-tone effect in thepicture. At the present. time it is barely possible to transmitsilhouettes. In the old spiral disk method, each succeeding hole wasplaced at a lower point in the frame, i. e., it scannedv the pictureframe at a lower portion than its predecessor. Consequently, twopictures taken, or framed, atdifferent points on the disk would be outof synchronism. Also the number of lines per picture was limited. by thenumberof holes that could bev placed around the periphery of the disk,and the number of holes was further limited by the fact that they had tobe a picture width apart. In the twin disk method described herein,there is no'diiference between one light permeable line a and its nextneighbor. The number of scanning lines, perpicture, therefore, is notlimited by the size of the disk or other medium. In the spiral hole diskthere is alimit to the size of the picture than can be scanned ortransmitted. Experts seem agreedthat three feet is the largestpracticaldisk that can be conveniently, or-practically rotated. Thelargest sized picture that can be transmitted or scanned by a three footdisk is two inches. This is due to the fact that at least forty eightholes placed a picture width (or two inches) apart will use all of theavailable space on the periphery of the disk. In the twin disk method,the only limit to the size of the picture is really the distortionproduced by the curvature of the disks, the pictures tending toassumethe form of partial segments of a circle, and also they are notplaced in a straight line but traverse the circumference of the circle.Those defects are, however, easily remedied by substituting tapes forthe disks, as described in this and'the previously identifiedapplications. Then there is perfect symmetry. By employing. a smallpicture frame, say one inch wide, on a three foot disk. there. would befifteen four-hundred-and-fifty line pictures'produced per second. If thedisk had twolight permeable lines per picture width, as 'shown at Figure3b and Figure 30, there would be fifteen nine-hundred-line pictures persecond. This would give as much detail as that possessed by a motionpicture. Then by projecting several images superposed on a screen, anydegree of image brightness desired could be obtained. Of course, tapesmaybe used. as media A and B, and indeed, motion. picture filmsphotographed in such manner that the light permeable areas are meretransparencies. may be used.

At the transmitting station, a plurality of images may be produced ofthe objects to be transmitted. Thus Figure 1 may be taken as arepresentation of the transmitter. The screen ID or H! may be then takento represent the objects to be transmitted. Several images are formed bylens or optical elements 9. Each image has a photoelectric cell in itsarea. The scanning devices A and B distribute the light pointssynchronously through the various image areas, and. consequently,photoelectric cells 5 are all actuated in synchronism to vary theelectric current in synchronism with the images. a high degree ofintensity to the signals, i. e., the image-varied electromagnetic wavesthat are being broadcasted. The principle of image duplication thusdescribed is available at the transmitter as well as at the receiver,and this means powerful, distinct television broadcasting.

Again referring to Figure 3c, in the top row M has partly intersectedwith a, as indicated by the arrow. In the second row it has traversedthreequarters of the course of a, and in the third row it has completedit, and b has commenced to traverse a; one line has been drawn orscanned and another is being drawn immediately next to it. In the fourthrow the arrow indicates that b has traversed almost the entire length ofa. In the fifth row, I) has started to traverse a, and b has finishedits passage over a. Thus, two lines have been drawn, and a third hasbeen started. It will be noticed that a has been shifting its coursegradually throughout, while I) has moved an entire picture width. :1,however, shifts its position uniformly and steadily and does not stopstill while 1), etc., traverse it, and then move on. Consequently, therewill be a slight deviation of the lines from the vertical. However, thiswill be so slight that it will not be noticed. As the scanned lines areshifting their position successively, there will be a visual image.There will also be a series of pictures, one in each frame, and theywill be in exact synchronism. As lines 1), etc., are so arranged thatbut one of them traverses line a at a time, and since a, etc., arespaced a picture width apart, there can be but one light point i in anyframe at a time. Consequently, no mask is necessary with thisarrangement. It also employs but two media. The pictures or images,since they are in synchronism may be superposedly projected upon ascreen or viewed by the eye directly, and thus any degree of brightnessmay be obtained by this super position.

The frames 7, f, f" (as many as desired) are movable laterally, and thusthe picture may be brought into frame by this movement. The frame at thereceiving station must be placed at a position corresponding to that atthe transmitting station with regard to media A and B, and photoelectricelements 5, whether they be photoelectric cells, or neon or other lamps.This framing process can be thus utilized also in bringing the pictureinto focus, i. e., into frame. For instance, A and B at the transmittingand receiving stations may be moving at exactly synchronous speeds, butthe light point in the frame at the transmitter may be located at adifferent point in the frame than the light point in the receiver frameis located. Lateral shifting of the frame may be utilized to remedythis. The contiguous frames 1, f, f", 1, etc., as many as desired, maybe made in one piece since the synchronizing of one image brings aboutthe synchronization of all with the image at the transmitting station.

This factor lends Having described my invention, I claim as new anddesire to procure by Letters Patent:

1. A scanning apparatus consisting of a plurality of optical imageforming means, a plurality of photoelectric .cells coacting with each ofsaid optical means, a plurality of differentially moving media bearingintersecting light permeable areas acting to produce a plurality oflight transmitting openings which traverses the elemental areas of saidimages synchronously, said light permeable areas on each of said mediabeing rectangular and parallel, and means for moving said media, saidphotoelectric cells acting to synchronously vary the intensity of anelectric current in accordance with said images.

2. The process of scanning which consists in forming a plurality ofsimilar images, synchronously and successively converting the elementalareas of said images into an image Varied current corresponding to saidimages.

3. A scanning apparatus which consists of two differentially movingscanning elements {each bearing a series of parallel, rectangular lightpermeable areas, said light permeable areas coacting'to form by theirintersections a plurality of light transmitting points, each of saidpoints acting to traverse the elemental areas of adjacent sections ofsaid elements, a plurality of optical elements forming similar images ineach of said sections and a plurality of photoelectric cells one in eachof said images and being acted upon by said light transmitting points toproduce an intense image-varied current.

4. A scanning apparatus consisting of two scanning media and means fordifferentially moving said media, a plurality of adjacent image areas,each of said media bearing a series of parallel rectangularlight-transmitting areas which by their intersections form a pluralityof light transmitting openings which synchronously traverse theelemental areas of a plurality of imagevarying light sources, aplurality of optical image forming means coacting with said lightsources to produce a composite image composed of a plurality ofsuperposed similar images.

5. A scanning apparatus consisting of two endless tapes' bearing lightpermeable areas, means for moving said tapes, one of said tapesembracing the other in the same plane, said tapes hearing each a seriesof parallel rectangular light permeable areas, a plurality of adjacentimage areas, a plurality of photoelectric elements supplied with acommon current on one side of said tapes and a plurality of opticalelements on the opposite side of said tapes, a reflector associated withsaid optical elements and a screen associated with said reflector.

6. A scanning process which comprises forming several images of anobject, simultaneously scanning the same points on said images,producing separate photoelectric currents by said scannings andcombining said currents to produce a single current.

ALOYSIUS J. CAWLEY.

